Staged turbine pump for liquefied gases



8 Sheets-Sheet 1 Fics. 1

E. ABRAMsoN STAGED TURBINE PUMP FoR LIQUEFIED GASES May 3, 1960 Filed March 22, 1956 INVENTOR Ernesc L.Abramson ATTORNEYS May 3, 1960 E. L. ABRAMsoN STAGED TURBINE PUMP FOR LIQUEFIED GASES 8 Sheets-Sheet 2 Filed March 22, 1956 INVENTOR Ernes: L.Abramson @4&4

ATTORNEYS May 3 1960 E. L. ABRAMsoN 2,935,026

sTAGED TURBINE PUMP FOR LIQUEFIED GASES Filed March 22, 1956 8 Sheets-Sheet 4 INVENT OR Ernes L.Abramson ATTORNEYS May 3, 1960 E. L. ABRAMsoN 2,935,026

STAGED TURBINE PUMP FOR LIQUEFIED GASES Filed March 2.2, 1956 8 Sheets-Sheet 5 Ernesc LAbrarnson BY I A ATTORNEYS May 3, 1960 E. .i ABRAMsoN 2,935,026

STAGED TURBINE PUMP FOR LIQUEFIED GASES INVENT OR Erness-Lhbramson ATTORNEYS May 3, 1960 E. L. ABRAMsoN 2,935,026

' STAGED TURBINE PUMP Foa LIQUEFIED GAsEs Filed March 22, 1956 4 8 Sheets-Sheet 7 'Fic-:L14 F1615 f F1616 F1617 INVENTOR Ernest L.Abramson ATTORNEYS -Many 3, 1960 E. l.. ABRAMsoN 42,935,026

STAGED TURBINE PUMP FOR LIQUEFIED GASES Q Filed March 22, 1956 8 Sheets-SheetB Fexl 124- L ZZ Wm supply ai low sarc pressure K insulacon l H l To discharge 99 ac elev asced, f" g Pressure -1 l J INVENTOR Ernes: L.Abramson ATTORNEYS This invention relates to staged turbine pumps, and particularly to such pumps when used to deliver gases in the liquid phase against substantial head pressures. As a basis of discussion, liquid oxygen Iwill be adopted as typical. It has a low boiling point at atmospheric pressure (minus 183 C.) and is highly volatile. From these facts arise serious problems.

The pump shaft must be sealed and the best available type of seal is a running seal with circulated liquid lubricant. Such lubricant must never enter the pump. To prevent contact of liquefied gas with the seal, and also to permit convenient thermal insulation of the pump, the pump is mounted with its shaft vertical and with the driving motor at the upper and the pump at the lower end of the shaft.

Below the motor and between grease seals is the upper ball bearing of the pump. This is of the combined thrust and radial type. Below the lower grease seal is a closed chamber in which are housed two reversely set running seals (disc seals) designed to prevent escape of oxygen along the shaft. The closed chamber has supply and discharge connections for the circulation through the chamber and in contact with the seals of a lubricant liquid (an ethylene glycol solution is one such liquid).

Next below the seal chamber is an oxygen chamber containing gaseous and liquid oxygen, and in the gas space a centrifugal liquid-slinger carried by the shaft and functioning to deliver to an intercepting cup any lubricant liquid which may flow downward along the shaft. A purge connection with valve is used, to detect the presence of liquid intercepted by the cup, to remove such liquid and to limit the outward (upward) pressure on the seals. The valve just mentioned is normally closed, but is opened for test and purging purposes.

One purpose served by the oxygen chamber is to keep liquid oxygen out of contact with the seals. This effect is dependent on the use of the vertical shaft, as will be explained.

Below the oxygen chamber is the pump housing.Y This arrangement makes it possible to surround the housing of the pump with a removable insulating shell, and favors the use of the above mentioned lubricant interceptors and purgers.

To prevent it from flashing into vapor, liquid must be supplied to the first stage of the pump under a moderate pressure head. It is desirable that this head be as low as practicable, and to that end, large Vinlet passages to the first stage are used. A static headl of about 36v inches of liquid oxygen is sufiicient.

To assure a maintained back pressure on theliquid in the first pumping stage, the normal delivery of that stage is made slightly greater than that of the second stage. This maintains pressure on the liquid as it enters the second stage and the second stage raises the pressure further. The third stage has a delivery rate which is approximately the same as that of the second stage and assists in delivery against the head pressure. In the second and third stages the operating pressure has reached a value at which the tendency of the liquid to flash into vapor no longer exists.

Fluid lubricants cannot be used within a liquid oxygen pump in contact with the oxygen and hence, within the pump, recourse is had to known types of dry self-lubricating bearing bushings.

atent The shaft, the enclosure of the oxygen chamber, the internal rings which denne the working spaces and the related flow passages, and the housing, are made of the same material (1S-8 stainless steel). Even so, the pump must be cooled down to its working temperature before it is started. This cooling is done by bleeding liquid oxygen into and through the pump an operation which requires twenty-five minutes and consumes about nine liters of liquid oxygen. The operation is attended by some unavoidable diierential expansion of the shaft and housing. Quantitative means are built into the pump to permit measurement of running clearances and assure centering of the impeller discs in the spaces in which they rotate before the pump is started.

The shaft and the pump housing are each suspended from above, the housing being sustained directly by the main frame and the shaft being sustained by the main frame. through the thrust bearing.

Thus the vertical shaft arrangement leads to practical advantages4 with respect to interception of liquid lubricant, and protection of the seals from extreme low temperatures and from contact with liquid gas.

A successful embodiment of the invention will now be described by reference to the accompanying drawings.

VIn the. drawings:

Figs. l, 2 and 3 when -assembled end to end in the order stated produce an axial section of the complete 3-stage pump, including the supporting frame, Fig. 1 showing the driving' connections and the upper bearing, which is of the combined thrust and radial type, Fig. 2 showing the seals, the interceptors for lubricant and the chamber used to control the pressure on the seals and Fig. 3 showing the pump. housing, the three rotors, the inserts or rings which define llow passages and working charnbers, and the lower bearing.

Fig. 4 is a front elevation of the main housing.

Fig. 5 is-a face View of the first stage runner.

Fig. 6 is an edge view of that runner.

Fig.. 7 is a perspective view of the micrometer dial.

Fig. 8' is a section on the line 8 8 of Fig. 11. In this View only the housing is sectioned, the rings and (Where visible) the runners being shown in elevation.

Figs. 9 and 10 are respectively top and bottom face views of the uppermost ring.

Fig. ll is a section on the line ll-l of Fig. 4.

Figs. l2 and 13 `are respectively top and bottom face views of the second (next to top) ring.

Figs. 14 and 15 are respectively top and bottom face views of the third (next to bottom) ring.

Figs. 16 and 17 are respectively top and bottom face views of the fourth (bottom) ring.

Fig. 18 is an elevation, showing in simplified form the pump with its functional connections. The outline of the heat insulating tub or munie is indicated.

Nora-In the description statements of direction will refer to the pump as positioned in Figs. 1-3 and also Fig. 18.

A supporting base-plate 21 carries a tubular pedestal 2.2 upon which the entire pump, and its motor drive are mounted. An electric motor 23 is mounted on top of the pedestal and drives through a coupling 24 the pump shaft 25 which is of corrosion resisting steel (stainless). Clamped between a shoulder 26 on shaft 25 and a nut 27 threaded on shaft 25 is the inner race of a combined thrust and radial ball bearing 28. The outer race of this bearing is urged against the bottom of a cup-shaped cage 29 by a threaded plug 31 reacting through spring 30 and follower 32. The spring 30 is a safety feature and its use is optional. The pump has been operated successfully with a rigid follower filling the interval between the plug and the race.

assume The shaft 25 passes through an axial opening in the bottom of cage 29 and an axial opening in plug 31. Conventional grease seals 33 are used above and below the ball bearing unit to prevent escape of lubricating grease. The cage 29 is threaded at 34 to the pedestal 22, so that the shaft may be adjusted in the direction of its axis by turning cage 29. A set-screw 35 engages anA annular groove whose width limits the range of adjustment. Screw 35 may be set up to fix the adjustment. The clearance space below the cage 29 is vented to atmosphere, as shown.

Since quantitative adjustments are needed an annular graduated dial 36 is adjustably held by clips 37 tothe pedestal and a coacting pointer 3S is adjustably mounted on cage 29. This is effected by connecting the pointer by screws 39 engaging plug 31 and passing through'arcuate slots in the pointer ring (see Figs. l and 7).

. This micrometer arrangement makes it possible to determine quantitatively both limits of axial clearance i at any existing temperature and then make a medial adjustment, i.e., the best one for that temperature. During cooling the pump for starting, adjustments must be made repeatedly because the clearances are small ascompared with the differential expansion. Differential expansion will occur, even between parts made of identical material, because different parts will change temperature at different rates. The micrometer head eliminates a risk of damage, which otherwise would be quite serious. Y

Between the pedestal 22, and the housing 41 of the pump it is necessary to have an adequate running seal against gas or liquid leakage from the pump and since such seals require liquid lubrication -it is necessary to provide means to intercept lubricant which may leak and tend to enter the pump, a risk existing particularly while preparing to start the pump.

The seal structure is mounted in a chamber 42 in the lower part of pedestal 22. The lower end of this chamber is closed by a plate 43 which is bolted to the central portion of the supporting base-plate 21 and sealed by a gasket `44. The seal comprises two complete units which are reversely set, one at the top of chamber 42 and the other at the bottom. Since they are duplicates the duplicated elements will be given the same reference numerals.

The fixed element is a ring 4S seated on a gasket 46 and held by a ring 47 held by studs and nuts as clearly shown in Fig. 2. The seal surface is an annular boss 48 which is lapped to a fine finish and is precisely normal to the axis of shaft 25. The rotary element is a cupshaped ring 49 which encircles the shaft and is sealed to the shaft by a gland 51 and packing 52, the ring and gland being constrained to rotate as a unit by pins 53.

The face of ring 49 which engages boss 48 is also a lapped surface normal to the shaft axis. The two rings 49 are driven and are urged into sealing contact with fixed seal bosses 4S by parts carried by an interposed ring 54 which is keyed to shaft 25 as indicated in Fig. 2. A circular series of sockets are formed in each of the two plane faces of ring S4 and house coil thrust springs 55 which surround drive pins 56. The sockets in one face of the ring alternate with those in the other. The construction is such that the rings 52 turn as a unit, but are spring-urged away from each other and hence towards coacting bosses 48. The connections 58 in pedestal 22, are for the circulation of a lubricant liquid, as will be explained later, with reference to Fig. 18.

The plate 43 serves as a closure for the lower'end of chamber 42. Actually it is a flange welded to the upper end of spacing tube 59. Another flange 60 is welded to the lower end of tube 59. The tube and both flanges are of stainless steel so that there will be no differential thermal expansion between the shaft 25 and tube 59. An examination-of the drawing will show that plates 21 and 43 and rings 45 are positively positioned by metal to metal contact, so that precision is assured. In this connection it should be observed that the rings 47 seat in metal to metal contact, so that rings 45 are precisely positioned.

Centered in tube 59 and spaced therefrom is a sleeve 61 which at about mid-height has a partition 62. An upstanding flange 63 surrounds shaft 25 and is spaced therefrom, so that the space around flange 63 serves as a liquid collecting cup. To permit withdrawing liquid from this cup apassage 64 leads from connection 65 to dip-pipe 66. The tapped holes 67 are for connecting pullers to sleeve 61.

Below partition 62 the sleeve 61 is perforated as indicated at68, so that the connection 69 communicates with the interior of sleeve 61. Set screws 71 lock sleeve 61 in position and are sealed against leakage by plugs 72.l

'CarriedV by shaft 25 above partitionr 62 is a conical slinger'73, sealed to the shaft 25 by 0-ring 74. The slinger 73 intercepts, and directs into the liquid collecting cup, any liquid which might flow down the shaft, particularly any lubricating liquid escaping from the seal chamber 42.

The housing proper 41 of the pump is formed of 18-8 stainless steel. The housing 41 has at its upper end a flange 75 and at its lower end a flange 76. The flange 75 is bolted to the flange 60 and the flange 76 serves as the means for attaching the annular ring-retaining member 77.

Fixed on the shaft 25 by means of keys shown in the drawing in dotted lines, are three bronze alloy turbine pump-runners, a first stage runner 78, a second stage runner 79 and a third stage runner 81. The first stage runner is mounted against a shoulder 82 formed on the shaft and is confined between this shoulder and a stainless steel spacer 83. The second stage runner 79 has an elongated sleeve-like hub 84 which extends in both directions from the runner. The third stage runner 81 has a sleevelike hub 85 which extends upward from the runner and engages the end of hub 84 which in turn engages the end of sleeve 83. A nut 86 threaded on the shaft 25 clamps the assemblage comprising the hub 85, the hub 84, the sleeve 83 and the first stage runner 78, between itself and the shoulder 82. A lock washer visible in the drawing is provided to lock the nut 86 so that it cannot loosen.

The housing 41 is bored to two different diameters to receive stainless steel rings. These are coaxial with each other and with the desired position of the axis of shaft 25.' These rings define the working chambers and flow passages. rfhe upper and smaller bore receives a top vring 87. The upper face of this ring is shown in Fig. 9.

This face has no function except as a`closure for the lower end of the space within the tube 59.

A second ring 88 is received principally in the smaller bore, but, at itsplower extremity, has a portion which fits the larger bore (see the shoulder at 89 in Fig. 3). The lowerV face of the first ring 87 and the upper face of the second ring 88 are shown respectively in Figs. l0 and 12 and are contoured to define the working space for the first stage runner 78. It will be observed that the centralportion of Fig. 12 is a mirror duplicate of Fig. l0. The fiow vpaths will be described later.

In the larger bore is a third ring 91. The working space for the second stage runner 79 is defined by the lower face of the ring 88 (see Fig. 13), and the upper face of ring 91 (see Fig. 14).

VThe fourth ring 92 also fits the larger bore. The lower face of the third ring 91 and the upper face of the fourth ring 92 are contoured to define the working space for the third stage runner 81. The configurations of these two faces are shown respectively in Figs. l5 and 16 and they are mirror duplicates.

The bottom face of the fourth ring is shown in Fig.

17.V It has tapped holes 93 to receive studs 94 which hold a fixed bearing housing 95. The lower bearing for the shaft 25 comprises a bearing bushing 96 of dry self `housing 95 and partly in `the ring 92.

ing-space at 121 and 122a ('see Figs. 15 and 16).

lubricating material which is housed partly in the bearing n It should be observed that the member 77 is annular in form and is -sealed to the housing 41 and to the ring 92 by an annular gasket 97. The extension 95 is distinct from the member 77 and is sealed to the ring 92 by the gasket 98. The shaft 75 is reduced in diameter where it fits in the bearing bushing 96. A by-pass connection 99 leads from the space below the lower end of the shaft 25 as will be hereinafter described in further detail.

The gasket 1 01 seals the upper end of the top ring 87 and flanges 60 and 75. A pin 102 fixes the position of the top ring 87 and the second ring 88 in the housing 41. Similarly, a pin 103 engages the second ring SS, the third ring 91 and the fourth ring 92 and xes their position.

A bearing bushing 104 of dry self-lubricating material (such as is used for bushing 96) is pressed into a central bore in the top ring 87 and lits the shaft 25 above the shoulder 82. A bushing 105 is pressed into the second ring 88. There is clearance between the bushing and the sleeve 83 and between the bushing and that portion of the hub 84 which is above the second stage runner 79. A bushing 106 is pressed into the third ring 91. It clears that portion of the hub 84 which is belowthe second stage runner and also the hub 85.

The inlet connection to the pump is generally indicated by the numeral 107 and the outlet connection by the numeral 108.

The first stage runner 78 is shown in face view in Fig. 5 and in edge view in Fig. 6. Near the periphery it has radial notches or buckets which increase in depth and width toward the periphery. These buckets are indicated by the numeral 109. They are cut in both faces of the rotor andv conform to accepted practice in the turbine pump art. In view of this fact and the clear illustration, it is deemed unnecessary toV elaborate the matter further. The other runners are similar.

The porting of the housing 41, and the rings 87, 88, 91 and 92 is shown in Figs. 3, 4 and 8-17 inclusive and will now be described. In this connection it should be remembered that statements of direction refer to Fig. 3. Figs. 4 and 8 show the housing 41 in the same attitude as does Fig. 3.

Another fact to be kept in mind is that the approach flow to the first and also that to the third stage runner divides into two branches, one above and the other below the runner, each branch then flows in an arcuate path in the direction of runner rotation and then turns toward .the other branch so that the branches approach the runner approximately tangentially on its opposite sides and so the liowing liquid engages the buckets smoothly. Approach flow to the second stage runner is inward toward the edge of the runner in a single stream that curves to merge into the path of the buckets. The shaft 25 turns clockwise as viewed in plan.

Refer first to Figs. 8 and 11 which show the housing and 10 and 12 which show proximate faces of the first and second ring which define the first stage working space. Liquid entering through connection 107 is divided by splitter 111 and flows into two branches 112, 113 which pass forward of shaft 25 and turn toward each otherat 112a and 113g where they enter the Working space. Discharge is at 114 to passage 115 in housing 41 through which flow is downward and to the right (see Fig. 11). The discharge from 115 to the second stage Working space is indicated at 116 in Fig. 4.

The working space for the second stage is shown in Figs. 13 and 14. The entrance is at 117 (see also Fig. 8) which registers with port 116 in the housing. The exit is at 11S and leads to passage 119 in the housing 41. This passage divides into two branches 121 and 122 which pass around arcuately in front of the shaft Z5 and their approach each other to enter the third stage work- Exit from the working space is at 123 and discharging liquid enters the discharge connection 108.

Comparison of Figs. 12, 14 and 16 will make it clear that the discharges 114, 118 and 123 are spaced around the shaft axis at approximately 120 intervals so that transverse stresses on the shaft approximately balance. Most of the liquid path affords rotary ow and this flow never reverses its rotary direction, so that eddy losses are reduced to the practicable minimum.

Variouslubricants for the seals may be used. A tank 124 (see Fig. 18) is connected by tubes 125, 126 with connections 5S, 58 to form a thermo-Siphon circuit. A 30% by weight solution of ethylene glycol has been used with success. One alternative is tricresyl phosphate.

The purge connection 65 leads to atmosphere through a valve 127, which is open only to purge or to test for leakage.

The upper by-pass connection 69 vents the oxygen chamber to the oxygen supply. It passes oxygen in the gaseous phase and also some liquid oxygen when the liquid level tends to rise. The rate of flow is controlled by a throttlng valve 123 which is set to establish a backpressure equal to about one fourth the pressure developed in the rst stage. A gauge 129 indicates the pressure in the oxygen chamber. The effect is to hold the liquid oxygen level at the line AB, which is at approximately the top of connection 69.

The lower by-pass connection 99 leads ythrough an insulated line to the liquid oxygen supply through an adjustable throttlng valve 131. The back pressure is indicated by a gauge 132. Insulation is used because the connection passes oxygen inthe liquid phase.

The two by-pass connections 69 and 99 cause limited flows of liquid oxygen through the upper bearing 104 and the lower bearing 96. p

The shaft 25, the tube 59, the housing 41, the rings 87, 83, 91 and 92 and the impeller-spacers have been described as composed of stainless steel. Stainless steel is a desirable material, but identity of material is the most significant consideration because it minimizes the tendency for differential expansion and contraction to occur. It could prevent differential expansion only while all parts are at the same temperature, a condition not attainf able in practice. Hence the micrometer indicator associated with the ball bearing is a subtle and important improvement. Of the above enumerated components the impellers are the least important so far as identity of material is concerned.

A further refinement is the use of alloys having a substantially Zero thermal coefficient such as a 36% nickelsteel alloy, for the par-ts enumerated in the preceding paragraph. This is a costly expedient and not necessary because the micrometer indicator simplifies the problem sufficiently for all practical purposes.

To start up the pump, the first` step is to check for running clearance and then permit liquid oxygen to flow through the pump until it reaches the temperature of the liquid. During the cooling down period frequent adjustments of the clearance must be made to correct for differential contraction and avoid damage to the impellers. As a rule the cage 29 has to be turned righthanded to lower the bearing and shaft 25. The amount of the adjustment can be read in thousandths of an inch on dial 36.

When the pump is thoroughly cooled a final adjustment of clearance is made. The bearing cage 22 is turned left-handed until the clearance limit is reached and the pump cannot be turned over by hand. The reading on the dial is taken, the bearing cage is turned righthanded to the other clearance limit and a reading on the dial is taken. The difference of the two readings is the total clearance. The mean setting between the two readings is made. The seal chamber 42 is then connected with lubricant supply tank 124.

The pump can now be started.

The drip cup intercepts leakage from seal chamber 42. Leakagemay occur during starting or stopping, but at other times will occur only if the seal has been damaged. The seal can be checked by opening valve 127 and should be checked at starting and from time to time during running. lf there is leakage from the seal, lubricant will discharge from line 65. lf there is no leakage, gas only will be discharged.

y The valves 127 and 1311 are cracked to discharge a little oxygen, so that some liquid will discharge along the bearing bushings 104 and 96. This increases the life of the bearings. Adjustment of valve 128 controls the pressure in the oxygen chamber in tube 59 and the liquid oxygen level in that chamber. The gas-filled space maintained in the upper part of that chamber protects the seals from contact with liquid oxygen and establishes conditions that assure the operation of the seals at a relatively higher temperature than that of liquid oxygen, which would be destructive.

The above considerations are the more important reasons for using avertical pump shaft, but a minor reason is the ease with which a protective muiile may be applied, and on occasion removed.

The use of the spring 30 has been described as optional. Its function is to reduce the risk of damage to the impellers during periods of cooling down and warming up before starting and after stopping. The running clearance is not increased, but the stressing which might be caused by differential expansion and contraction in lthe event of faulty manipulation is limited.

While the best known embodiment, one proved by successful test, has been described in detail, this embodiment is illustrative. The scope of the invention is defined in the claims.

What is claimed is:

1. A turbine pump for developing pressure on and for propelling liquefied gases, comprising in combination, a substantially vertical rotary shaft having impelling means mounted thereon; a housing enclosing at least one working space for said impelling means, said housing having near its upper end an inlet connection leading from a source of liquid gas at low pressure, the housing having near its lower end a discharge to a point at relatively high pressure; a chamber-enclosing upward extension of said housing adapted to confine gas and liquid in contact with each other, said shaft extending through said chamber; bearings for said shaft, one. enclosing the lower end of the shaft and the other interposed between the upper end of the housing and the lower end of the chamber; sealing means resisting leakage around said `shaft where it emerges from the upper end of said chamber; and a valved by-pass connection leading from said chamber at approximately the desired level of liquid gas therein to the source of liquid gas whereby pressure in the chamber and effective on said sealing means may be limited.

2. A turbine pump for developing pressure on and for propelling liquefied gases, comprising in combination, a substantially vertical rotary shaft having impelling means mounted thereon; a housing enclosing at least one working space for said impelling means, said housing having near its upper end an inlet connection leading from a source of liquid gas at low pressure, the housing having near its lower end a discharge leading to a point at relatively high pressure; a chamber-enclosing upward extension of said housing adapted to confine gas and liquid in contact with each other, said shaft extending through said chamber; bearings for said shaft, one enclosing the lower end of the shaft and the other interposed between the upper end of the housing and the lower end of the chamber; sealing means of the liquid lubricated type resisting leakage around said shaft where it emerges from the upper end of said chamber; a valved by-pass connection leading from said chamber at approximately the desired level of liquid gas therein to 8 Y the source of liquid gas; an intercepting cup in said chamber above the level of liquid gas therein; a rotary slinger mounted on the shaft and serving toV divert liquid lubricant, should it flow down the shaft, centrifugally into said cup; and a valved purge connection for draining liquid from said cup.

3. A turbine pump for developing pressure on and for propelling liquefied gases, comprising in combination, a substantially vertical rotary shaft having impelling means mounted thereon; a housing enclosing at least one working space for said impelling means, said housing having near its upper'end an inlet connection leading from a source of liquid gas at low pressure, the housing having near its lower end a discharge leading to a point at relatively high pressure; a chamber-enclosing upward extension of said housing adapted to confine gas and liquid in contact with each other, said shaft extending through said chamber; bearings for said shaft, one enclosing the lower end of the shaft and the other interposed between the upper end of the housing and the lower end of the chamber; sealing means resisting leakage around said shaft where it emerges from the upper end of said chamber; a valved by-pass connection leading from the chamber at a level near the bottom thereof to the source of liquid gas; and a valved by-pass connection leading from a point within the lower bearing below the lower end of the shaft to the source of liquid gas.

4. A turbine pump for liquefied gases comprising in combination a pump housing having an inlet connection leading from a source of gas in the liquid phase at low pressure, and a discharge leading to a point of delivery at relatively high pressure, said housing having an upward extension enclosing a chamber adapted to confine gas and liquid in contact with each other; a rotary shaft which extends substantially vertically through said housing, through said chamber and out through the end of the chamber remote from said housing; upper and lower bearings in the pump housing and serving to support said shaft, the said upper bearing also serving to separate the interior of said housing from said chamber, and the lower bearing enclosing the lower end of said shaft; a seal surrounding said shaft where it emerges from said chamber; two valved bleed connections leading to said source, one from said chamber approximately at the liquid level therein and the other from the lower end of said lower bearing; and an interceptor for liquid which may tend to flow down said shaft, and located in said chamber above the liquid level therein.

5. The combination delned in claim 4 in which the interceptor comprises means for retaining in the chamber an annular bath of liquid surrounding and radially spaced from the shaft, and rotary, crowned slinger which extends beyond the inner margin of said bath and delivers thereto when the shaft rotates and also when it is at rest.

References Cited in the le of this patent UNITED STATES PATENTS 1,027,947 Wedge May 28, 1912 1,515,816 Smith Nov. 18, 1924 1,570,285 Schleyer lan. 19, 1926 1,736,002 Frickey et al Nov. 19, 1929 1,910,811 Peterson May 23, 1933 2,056,553 Abramson Oct. 6, 1936 2,075,895 Harmon Apr. 6, 1937 2,237,027 Dorer Apr. 1, 1941 2,250,714 La Bour July 29, 1941 2,406,947 Harlamoff Sept. 3, 1946 2,426,645 Riede Sept. 2, 1947 2,427,656 Blom Sept. 23, 1947 2,468,246 Thayer Apr. 26, 1949 2,658,454 Greene Nov. 10, 1953 2,684,034 Roth July 20, 1954 2,693,761 Mylting Nov. 9, 1954 2,730,954 Hornschuck Jan. 17, 1956 2,764,943 Peters Oct. 2, 1956 

